XML : ViewPager sends NullPointerException after AndroidAnnotations

Good day. I have added AndroidAnnotations to an existing project. Prior to adding the plugin, it worked like a charm.

After it, I'm getting a NullPointerException on a ViewPager.

Here is my main_activity.XML

  <?xml version="1.0" encoding="utf-8"?>  <RelativeLayout      xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_width="match_parent"      android:layout_height="match_parent"      android:background="@color/primary"      android:orientation="vertical">    <android.support.v4.view.ViewPager      android:id="@+id/main_act_vp"      android:layout_width="match_parent"      android:layout_height="match_parent" />    <Button      android:id="@+id/main_act_btn"      android:layout_marginBottom="55dp"      android:layout_marginRight="100dp"      android:layout_marginLeft="100dp"      android:layout_width="match_parent"      android:layout_height="58dp"      android:textColor="@color/white"      android:textSize="14sp"      android:gravity="center"      android:background="@drawable/button_border"      android:text="@string/description_button_knowmore"      android:layout_alignParentBottom="true"      android:layout_centerHorizontal="true" />    </RelativeLayout>    

And here is my MainActivity, where I'm injecting the ViewPager:

  @EActivity(R.layout.main_activity)  public class MainActivity extends FragmentActivity {        ....        @ViewById(R.id.main_act_vp)      ViewPager main_activity_viewPager;        @Override      protected void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);        FragmentStatePagerAdapter main_act_adapter =              new FragmentStatePagerAdapter(getSupportFragmentManager()) {          @Override          public Fragment getItem(int position) {              switch (position) {                  case 0:                      return new ObFirst_();                  case 1:                      return new ObSecond_();                  case 2:                      return new ObThird_();                  default:                      return null;              }          }          @Override          public int getCount() {              return 3;          }      };        main_activity_viewPager.setAdapter(main_act_adapter);        ....  }    

And here is the error I get

  FATAL EXCEPTION: main  Process: com.avena.avenafit, PID: 14218  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.avena.avenafit/com.avena.avenafit.onboarding.MainActivity_}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  at android.app.ActivityThread.access$800(ActivityThread.java:151)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:135)  at android.app.ActivityThread.main(ActivityThread.java:5254)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference at     com.avena.avenafit.onboarding.MainActivity.onCreate(MainActivity.java:148)  at com.avena.avenafit.onboarding.MainActivity_.onCreate(MainActivity_.java:39)  at android.app.Activity.performCreate(Activity.java:5990)  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  at android.app.ActivityThread.access$800(ActivityThread.java:151)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:135)  at android.app.ActivityThread.main(ActivityThread.java:5254)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)    

What do you guys think could be the problem?